Apparatus for handling viscose solutions



April 13, 1948. H.-O. DAVIDSON APPARATUS FOR HANDLING VISCOSE SOLUTIONS Filed March 1, i944 INVENTOR.

ATTORNEY Patented Apr. 13, 1948 UNITED STATES PATENT OFFICE APPARATUS FOR HANDLING SOLUTIONS VISCO SE Hobart 0. Davidson, Swarthmore, Pa., assignor to American Viscose Corporation, Wilmington, Del., a corporation of Delaware Application March 1, 1944, ScriaI No. 524,583

7 Claims.

This invention relates to apparatus for handling viscose solutions. More particularly the invention has to do with the viscose during the ripening and the handling or feeding thereof to the product-forming room. The invention will In the conventional practice of today, batches of cellulose xanthate are dissolved in an aqueous caustic solution and three or four such charges blended to form a final viscose charge. These charges are sent to the ripening room, where they are confined in tanks, forced, usually by air pressure, through a filter press into other tanks, filtered, confined in the other tanks, and the processes of filtering and confining repeated until the viscose has reached the stage of ripeness suitable for delivery to the room wherein it is to be formed into the desired products. When this stage has been reached, the viscose charge is flowed into one of two or more "feed or spinning tanks, from which it is delivered to the product-forming room. The viscose is forced from one feed tank, usually by air pressure or by positive displacement pumps, which may be assisted by air pressure on the tank,

until the tank is substantially exhausted, then viscose is taken from the other feed tank or tanks, and so on.

In accordance with the present invention, the transferring of the viscose during ripening in succession through several filters and several groups of tanks is eliminated. Instead a large battery of ripening tanks are filled in rotation with the blended viscose which is then allowed to stay in these tanks until ripened to the proper extent, after which the ripened viscose is withdrawn in rotation from these storage tanks ber of ripening tanks as compared to the number of feed tanks are needed, because of the long periods of ripening, usually several days, required. The present invention provides a system for making it practical and economically feasible to handle the viscose in such a large number of tanks without encountering pumping difficulties resulting from long suction lines, and difiiculties resultingfrom stagnation of the viscosein remote parts of the piping system, while withdrawing viscose from a given ripening tank. The present invention has the advantages of reducing the amount of handling and pumping of the viscose during ripening, and of requiring relatively less equipment and supervision. It provides for blocking off a group or groups of the ripening tanks for drainage, cleaning, and refilling, while maintaining the circulation of viscose having a substantially uniform degree of ripeness through all pumps, and substantially all of the remainder of the piping system. It also delays filtration to permit the maximum agglomeration of filterable products, after which it is most effective.

The invention can best be understood by referring to the accompanying drawing, of which- Figure 1 is a diagrammatic view of the piping system; V

Figure 2 is a diagrammatic view showing one form of relief valve thatmaybe used in accordance with the invention; and

Figure 3is a diagrammatic view of a modified arrangement.

In Figure 1 there are shown a plurality of ripening tanks numbered 1 to 15. These tanks are fed from the viscose dissolvers by the header [6 and the branch lines [1 connected to the header by cocks I8, which are three-way except for that connecting the last tank l5, which is two-way. For discharging these tanks, they are associated in groups with separate headers.

The number of groups may vary from two to five or more, and the number of tanks in each group may vary from three to six, more or less. As shown, however,there are three groups, each comprising five tanks associated with the headers i9, 20 and 2| respectively. Cocks 22, which are all of three-way type, except for the twoway type used for the tanks connected t-othe end of the headers, connect the discharge lines 23 from the tank bottoms to their respective headers. Eachtank may be provided with a dump valve (not shown) at its bottom, which may be turned to connect or disconnect the tank proper from its discharge line =23.

Separate positive displacement pumps 24, 25 and 2B are connected to the respective headers 19, 20 and 2|, throughtheir suction lines 21, 28 and 29, and discharge into a common line 36,

which, as shown, doubles back on itself and leads to the filter 3|. Another positive displacement pump '32 is connected between the discharge line 33 of filter 3i and the feed line 34 to a second filter 35 which discharges through line 36 connected to the suction side of pump 31, which discharges through line 38 into a third filter 39 from which a discharge line 40 may-lead to the feed tanks I40 or through additional filtering equipment. The filters may be graduated so that each succeeding filter removes finer aggregates, though this is not essential.

By-pass lines 4|, 42 and 43 connect the com- 4 the intermediate tanks of agiven group, so that can readily be determined when a given tank and section of the header has been drained. There is specifically shown in Figure'l the sight glasses l2, l3 and 14, just in advance of the cocks 4|, 42' and 43'. Sources of light 15 are provided on one side of the sight glasses, whileelectric eyes 16, ll and 1'8 on the other side are provided with suit able conventional relays and connections with their respective main driving motors and idling motors and connections 4|, 42 and 43' so that i when a given header has been drained, the main mon discharge line at points thereinbeyond. all of the pumps 24, 25 and 26 tattle-respective. pump suction lines 21, 28 and 29 through three-way cocks M, 42' and 43'. These by-pass lines contain valves 44, 45 and 46, which serve as relief valves as well as by-pass valves. These. valves may be hydraulically operated and are controlled by the pressure-responsive. controller 41 which is connected to line 33. This controller 41 may be of the conventional type which opens. a valve in an air line 48 (shown dotted) when the pressure in line 33. exceeds a. predetermined value to which the controller is set, and thus. permits air to flow to the hydraulicrelief valves 4.4", 45 and 4.6 through the air lines 49,. 541, and 52..

A by-pass line- 53connectsthe pump discharge line 34- with the pump suction, line 33, ahydraulically-operable relief and by-pass valve 54 being provided. therein. A controller 55 connected. to line 36 is responsive to the pressure therein and operates the relief valve by ad-mitting air to line 56 when the pressure in; line 36 exceeds a predetermined value to which the controller is. set.

Figure 2 hows diagra-mmaticallythe hydraulically operated relief and by-passwalve, which is the same as those used 94745, 46 and 54. The valve has ports 30' and 21' which are connected to lines 38 and 21 respectively. Port 30 opens into port 2'!" at 51 and 58,, the latter opening being provided with a seat against which the valve 59 is normally pressed when closed. The valve stem 60 carries. a. piston 61 which is normally urged'by the spring 62 to close the valve, but which is forced to open the valve whenair is admitted through the connection 50' with. airline 50.

The small opening 51 serves to by-pass. a: small amount of viscose constantly.

Constant speed motors: diagrammatically shown at 63, 64 and 65 are provided to drive the pumps 24,. 25 and26, respectively. These motors are preferably adjustable to: any speed, so that any predetermined volume of viscose can be'delivered thereby, and they are connected to the pumps by means of overdrive clutches-.so that small idlin motors diagrammatically shown at 6B, 61 and es, can: operatethe pumps at slow speed when the main driving motors 63,. 64 and 65 are not in use. Alternatively each of the pumps 24, 25 and 26 may be connected to a. constant speed motor through a reduction gearing transmission by which the pump may be driven alternately at high. or low speeds when and as desired.

Constant speed motors 32' and 3'!" which are preferably adjustable in speed drive the pump 32 and 31 respectively.

Each discharge header [9, 29 and 2;!- and'. its associated line 21, 28 and 24, may be providedrw-ith an off-line drain. valve, or cock 69:, and Hv respectively. Sight glasses may be provided at any point in the headers 49,. 2B; and il, such as on the far side (with. respect to the pump) of each of driving motor is stopped, the idling motor is started, and the respective cock is blanked toward the header while permitting flow through the respective by-pass line.

A modification of the arrangement of tanks and pipe lines is shown in Figure 3, in which the important parts corresponding to those shown in Figure 1 are designated by the same reference characters as in Figure 1, with the addition of the postscript a.

The. operation is asfollows: Dissolved viscose is delivered in. rotation to the ripening tanks, illustratively in the order of their'numerical designations. When ripening has. proceeded to such an. extent that withdrawal from each of the tanks in sequence is in order, the cooks in the headers, except. that associated with the first tank filled, which is tank I in the present instance, are blanked toward their tanks; cock-4i. is turned to connect the header IS, the by-pass line il, and the pump 24; and the main driving motor 63 operates the pump 24. Cocks 42 and- 43' are turned to blank ofi their respective headers 20. and 2| while connecting the by-pass lines 42- and '43 with thepumps 25 and 26, Which are operated at low speed by the idling motors 61 and 6% Each of the pumps 24, 25 and 26- and 32 is ad'- justedto deliver when driven by its respective main driving motor somewhat more than pumps 31, the excess in each casebeing discharged the respecsmall positive pressure in thesuctionside of pump 3.1 by operating relief valve 54' when the pressure at that. point. exceeds. the. predetermined value. Similarly a small constant. positive pressure is maintained on the. suction side of pumps 32 by the controller 4T which operates one or more of the relief valves 44, 45 and 46 when the predetermined pressure is exceeded. It will thus be seen that series filtration is obtained with controlled pressure on each filter just suificient to operate the filter at the desired'rate of flow. Pump 3 1, of course, determines the rate of filtration.

Thus. each of the first group of tanks will be emptied in succession, upon the conclusion of which the header [9 is drained, cock 4 I is blanked toward the header, leaving the by-pass 4| open to the pump 24. The main motor'63 is stopped and motor 66' is started. The cocks in headerZll are then set, so that tank 8 can be drained through cock 42. which also is open to the. by-pass line 42. Motor 64 then operates the pump 2.5.

After emptying the second group of tanks, withdrawal is performed in similar fashion from the tanks in the first or any additional groups.

While withdrawal ismade from onegroup of tanks, the tanks in other groups may be refilled, cleaned and drained through the ofi-linevalve corresponding to 69, 10, or H, and repaired, or.

dling viscose in .a large number oftanks in accordance with which positive displacement pumps with relatively short suction line's-are provided fortforcing the substantially completely ripened viscose through a series offiltersl There is also provision for controlling the'pressure on a series of filters to maintain the minimum pressure on i" the filters that is neededat any time during the filtering cycle to operateat the desired flow, and thus correlating the fiow through the several filters to obtain efficient and economical filtration at a substantially uniformrate of flow. In addition, there is provision for continuous circulation of the viscose through all parts of the system at all times except when one or more of the groups of tanks are blanked off after drainage, for refilling and the like. "In this way there is no opportunity for stagnation: of viscose in any portion of the system. i

Certain subject matter other than that claimed herein is the subject of claims in applicants copending application Serial No. 601,901, filed June 27, 1945.

It is to be understood that changes and modifications may be made without departingi'rom the spirit of my invention, as defined in the appended claims.

I claim:

1. Apparatus for handling dispersions of viscose and other materials subject to change in properties with passage of time preparatory to delivery to the product-forming stage comprising a large number of tanks, at least two discharge headers, each of the headers being associated with a separate group comprising a plurality of the tanks, a common header, separate branch lines connecting the respective discharge headers to the common header, pumping means in eachof said lines, separate by-pass lines connected to the respective branch lines on the suction side of the pumps therein and to the common header beyond all of the branch line connections thereto.

2. Apparatus for handling dispersions of viscose and other materials subject to change in properties with passage of time preparatory to delivery to the product-forming stage comprising a large number of tanks, at least two discharge headers, each of the headers being associated with a separate group comprising a plurality of the tanks, filtering means, a common header connected to the filtering means, separate branch lines connecting the respective discharge headers to the common header, pumping means in each of said lines, separate by-pass lines connected to the respective branch lines on the suction side of the pumps therein and to the common header beyond all of the branch line connections thereto.

3. Apparatus for handling dispersions of viscose and other materials subject to change in properties with passage of time preparatory to delivery to the product-forming stage comprising a large number of tanks, at least two discharge headers, each of the headers being associated with a separate group comprising a plurality of the tanks,

filtering means, a common header connected to "6 common header, pumping means in each of said lines, separate by-pass lines connected to the respective branch lines on thesuction side of the pumps therein and to the common header beyond all of the branch line connections thereto, means for selectively shutting off any of the discharge headers from its associated pumping means without shutting'ofi the by-passline from the re-, spective pumping means, means for selectively opening any of the tanks to its associated header, means for'selectivelydriving any of the pumps at one speed for emptying the tanks and means for selectively driving any of the pumps at a lower speed for circulating a portion of the dispersion through the by-pass during periods when another of the pumps is emptying a tank of another group.

4. Apparatus for handling dispersions of viscose and other materials subject to change in properties with passage of time preparatory to delivery to the product-forming stage comprising a large number of tanks, at least two discharge headers, each of the headers being associated with aseparate group comprising :a plurality of the tanks, a plurality of filtering means, pipe-lines connecting the filtering means in series, a common header connected to discharge into the first filtering means, pumping means connecting the discharge headers with the common header, additional pumping means for feeding each filtering means beyond the first from the discharge of the preceding filtering means, by-pass lines connecting the discharge side of the pumping means beyond each filtering means except the last with the suction side of the respective pumping means and means for controlling the discharge pressure of each filtering means except the last.

5. Apparatus for handling dispersions of viscose and other materials subject to change in properties with passage of time preparatory to delivery to the product-forming stage comprising a large number of tanks, at least two discharge headers, each of the headers bein associated with a separate group comprising a plurality of the tanks, a plurality of filtering means, pipelines connecting the filtering means in series, a common header connected to discharge into the first filtering means, pumping means connecting the discharge headers with the common header, additional pumping means for feeding each filtering means beyond the first from the discharge of the preceding filtering means, by-pass lines connecting the discharge side of the pump ing means beyond each filtering means except the last with the suction side of the respective pumping means, and means for maintaining predetermined substantially constant pressures on the suction sides of each of the pumping means except that in advance of the first filtering means.

6. Apparatus for handling dispersions of Viscose and other materials subject to change in properties with passage 0f time preparatory to delivery to the product-forming stage comprising a large number of tanks, at least two discharge headers, each of the headers being associated with a separate group comprising a plurality of the tanks, a plurality of filtering means, pipelines connecting the filtering means in series, a common header connected to discharge into the first filtering means, separate branch lines connecting the respective discharge headers to the common header, pumping means in each of said lines, separate by-pass lines connected to the respective branch lines on the suction side of the "7. pump therein and tozthe common header beyond'all of the branch line connections thereto, additional pumping means for feeding each filtering means beyond the first fromthe discharge of the preceding filtering means, by-pass lines connecting the discharge side of each of the additional pumping means except the last with the suction side of the respective pumping means, and means for controlling the discharge pressure of each filtering means except the last.

7. Apparatus for handling dispersions of viscose and other materials subject to change in properties with passage of time preparatory to delivery to the product-forming stage comprising a large number of tanks, at least two discharge headers, each of the headers beingassociated with a separate group comprising a plurality of the tanks, a plurality of filtering means, pipelines connecting the'filteling means in series, a

common header connected to discharge into the first filtering means, separate branch lines connecting the respective discharge headers to the common header, pumping means in each of said lines, separate -by-pass lines connected to the respective branch lines on the suction side of the pump therein and to the common header-beyond all of the branch line connections thereto, additional pumping means for feeding each filtering The of this patent nected to the discharge line of "the respective filtering means responsive to pressureytherein connected to the relief valve toopen it when a predetermined pressure is exceeded in saidfdischarge line.

- HOBART-C). DAVIDSON. v

, REFERENCES CITED The following references are '01 record in the UNITED ,STATES PATENTS Number Name 7 1 Date 1,877,337 Kampf et a1 -Sept. 13; 1932 1,895,192 Kampf 'Jan. 24, 1933 2,232,326 Helm Feb. 18,1941

Freudenberg et al. Nov. 5, 1940 

